Rigidbody2D random asteroid rotation

Hello,
I want to use this code to random rotate a spawned asteroid but it is not working (Unity 5.0.2)

using UnityEngine;
using System.Collections;
    
public class RandomRotator : MonoBehaviour
{
	public float rotation;

	void Start()
	{
		rigidbody.angularVelocity = Random.value * rotation;
	}
}

MonoDevelop can’t see “rigidbody” property and aslo angularVelocity

thanks

// EDIT:

solved!

public float speed;
private Rigidbody2D rigidbody2d;

void Start()
{
	rigidbody2d = GetComponent<Rigidbody2D>();
	rigidbody2d.angularVelocity = Random.value * speed;
}

See:

http://docs.unity3d.com/Manual/ControllingGameObjectsComponents.html